Add metrics-server-operator

[atoato88]

This PR adds metrics-server-operator to examples/.
As of now dashboard-operator is located in examples/.
Dashboard v2.0.0 which is next release can use metrics-server for
monitoring statistics of k8s nodes.

It's better to add metrics-server-operator to this repo because that
dashboard v2.0.0 will release before long.

When dashboard v2.0.0 has released, it is needed to add v2.0.0
manifests to dashboard-operator.

[atoato88]

/assign @johnsonj
Could you review this?

[johnsonj]

Something to consider: This could also live in kubernetes-sigs/cluster-addons. It may also make sense to duplicate the dashboard-operator there?

Overall looks good, please address the super-minor assign copyright comment.

[johnsonj]

I think The Kubernetes Authors is standard?

[atoato88]

Thank you for comment. I've fixed these.

[johnsonj]

Thank you @atoato88 !

[johnsonj]

/lgtm
/approved

[johnsonj]

/approve

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[atoato88]

@johnsonj
Thank you for approving!!

I also thought what you considered. 😃
dashboard-operator and metrics-server-operator in this repository is examples for this framework.
But the same time, it is reasonable to place in kubernetes-sigs/cluster-addons because of it's truely addons. 😃

As you comment, we can move these to kubernetes-sigs/cluster-addons.
But I think that it should not be duplicated to two places(kubebuilder-declarative-patterns/examples/ and cluster-addons/) becuase of avoiding double management.
WDYT?

Should we use git submodule?

1. move codes(relating to dashboard-operator and metrics-server-operator) in kubebuilder-declarative-patterns/examples to cluster-addons repository
2. remove directory examples on kubebuilder-declarative-patterns
3. on kubebuilder-declarative-patterns, git submodule add https://github.com/kubernetes-sigs/cluster-addons.git examples

But this may need some code changes import in *.go files and go.mod.

Or, is git submodule something tricky?

[johnsonj]

I think you nailed it that dashboard is an addon and duplication is bad news. Submodules are tough to manage. If we want to make the dashboard-operator useful (and not just an illustrative example of how to use this library) then I think it just doesn't belong here.

What about a wilder turn:

1. Move {dashboard, metrics-server}-operator to cluster-addons
2. Replace dashbboard-operator with something where we don't care about versions, like guestbook-operator (as in this guestbook or the go version). We can just use it to show 'how it's made'

[atoato88]

I agree with your idea. 👍
It's a reasonable suggestion.